1. Field
This disclosure relates generally to semiconductors, and more specifically, to semiconductor circuits which use one time programmable memories.
2. Related Art
A category of memory devices in semiconductor technology is known as one time programmable (OTP) memory. There are various known instantiations of an OTP memory element including an electrical fuse or eFuse. eFuses are generally programmed by forcing a large electrical current through them. The high current is intended to alter the eFuse structure which results in a high resistance state. For conventional eFuse programming, the eFuse structure to be programmed is typically selected by a decoded address which is generated by a controller circuit.
With conventional eFuses, there is a risk that the eFuse may be inadvertently programmed by spurious signals. Such spurious signals may originate from a variety of sources, such as during a circuit power up, during testing and from radiation induced upsets. There is also a risk that the eFuses are falsely programmed during a circuit power cycle when it is possible that the control circuit of a matrix of eFuses is in an undefined state due to power sequencing issues. As a result, if the controller issues short, erroneous signals, the eFuse array may be briefly driven into a write state. In this state, inadvertent programming of one or more eFuses will occur. Additionally, users of products are instructed to avoid certain system operating conditions which can inadvertently program an eFuse. However, various customer systems use operating conditions which nonetheless create inadvertent programming of eFuses.